Digital displays have the advantage of furnishing an unequivocal indication of the measured value without the necessity of interpolation. However digital displays are not particularly suitable when changes in the measured value are to be noted. For such applications, it has up to now been necessary to add an analogue instrument to the digital display. The use of two indicators or displays increases both the cost of the equipment and the required space.
A particular field of application of the present invention is the field of electronic scales. The problem it solves arises, for example, when a substance on the scale is to be increased until its weight reaches a desired value. Other applications include any measuring instrument in which rapid changes in the indicated value must be noted by the operator and/or when some manipulation by the operator must result in the achievement of a predetermined desired value. This problem can, for example, arise in machine tool operation when the path of a member of the apparatus is prescribed and any deviations from the path are to be noted. The present invention can also find application in those cases in which it must only be determined whether a measured value is below, within, or above a predetermined value range. Under all such circumstances a digital display constitutes an unnecessary strain or cannot be interpreted at all.